biol270chap_5 - Chapter 5 Chapter The Human Population...

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Unformatted text preview: Chapter 5 Chapter The Human Population Human Population Growth and the Consequences the Human population expansion and its cause Different worlds Consequences of population growth and affluence Dynamics of population growth. Human Population Expansion and Its Cause Its Reasons for the patterns of growth • Biotic potential exceeds environmental resistance: birth rates exceed death rates There are 6.3 billion people on Earth If each one stood up, pronounced their name and sat down • It would take 600 years to complete roll call • By 2025 it will take 1,000 years to complete this exercise World Population Over the Centuries Centuries 9,000 human beings added to the planet every hour Reasons for the Human Population Explosion Population Expanded resource base Causes of disease recognized Improvements in nutrition Discovery of antibiotics Improvements in medicine Increase in number of women who actually reach child­bearing age (total fertility rate) Changing Human Survivorship Curves: Went From B to A Curves: A % Survival B Birth Age Death Population Projections Based on Different Fertility Assumptions Different Gradual decline in fertility in developing countries. 2.02 children/woman ½ child lower than medium projection ½ child higher than medium projection Maintain fertility rate of 2.6 children/woman Average Number of Children, Grandchildren, and Great Grandchildren Grandchildren America West Germany Africa • • • 14 5 258 Different Worlds Different Rich nations, poor nations Population growth in rich and poor nations Different populations, different problems Major Economic Divisions of the World World Gross national income/capita Economic Categories Based on Per Capita Gross National Income (see Fig. 5-4) Fig. High­income, highly developed, industrialized countries. • United States, Japan, Canada • Average GNI per capita = $26,710 Economic Categories Based on Per Capita Gross National Income (see Fig. 5-4) Fig. Middle­income, moderately developed countries • Latin America, South Africa, China • Average GNI per capita = $1,850 Economic Categories Based on Per Capita Gross National Income (see Fig. 5-4) Fig. Low­income, developing countries • • Western and central Africa, India, central Asia Average GNI per capita = $430 Disparities Disparities Developed countries • • • • Low­income developing contries 15% of the world’s population Control 80% of the world’s wealth Difference in per capita income: 63 to 1! 37% of the world’s population Control 3.0% of the world’s gross national income Dimensions of the Human Poverty Index Index Different Populations, Different Problems Problems Human pressure on the environment caused by three factors. • • • Population size Affluence Technology Different Populations, Different Problems Problems IPAT Formula: calculates human pressure on the environment (I = P x A x T) • • • • I = environmental impact P = population A = affluence and consumptive patterns T = level of technology in the society Different Populations, Different Problems Problems Environmental impact of developing countries due to “P.” Environmental impact of developed countries due to “A” and “T.” • Both have some measure of “I” for different reasons. • Average American places at least 20 times the demand on Earth’s resources compared to a person in Bangladesh. Different Populations, Different Problems Problems How does stewardship (S) effect the IPAT formula? • S = wildlife conservation, pollution control, energy conservation, and recycling I=PxAxT S Population Increase in Developed and Developing Countries and currently 82% est. 90% 2075 Population Data for Selected Countries (Table 5-2) Countries Country World Developing Countries Developed Countries Total Fertility Rate (aver. no. of children / woman) Doubling Times (Years) 58 47 700 2.7 2.9 1.6 Global Conditions for a Sustainable Population Sustainable Lower fertility rates (stabilize population) Consumption must decrease Protect the environment (stewardly action must increase The Developing Countries The Post World War II vaccines and antibiotics introduced (Cold War) • Death rates decreased • Rapid population growth Most of the population dependent on small scale farms • Stress on governments and environment Consequences of Exploding Populations in the Developing World World The Developing Countries The 1) Reform the system of land ownership 20th century communism ­ Collectivization • Inefficient 19th & 20th century colonialism – ownership by wealthy few • Inequality The Developing Countries The 2) Intensify cultivation of existing land to increase production per unit area Many soils will not support increased production • Historically used rotation to replenish soils (more sustainable) • No rotation­ increased soil erosion & synthetic fertilizers required (less sustainable) The Developing Countries The 3) Open new land to farm Not sustainable­ only so much arable land Best land already in production (cultural drivers) Continued loss of ecosystem services The Developing Countries The 4) Illicit activities Grow a crop with a higher return • e.g., Opium poppy (heroine), Marijuana, Coca (cocaine) The Developing Countries The 5) Move to cities and seek employment Extremely high densities • Extreme poverty • Non­functional governments (lack of basic services) • Political/social instability The Developing Countries The 5) Move to other countries xenophobia (fear or contempt of strangers or foreign people) Replacement migration (+) • Developed countries need population growth for continued economic growth Growing Cities Growing Consume the largest share of 11 or 20 major commodities Eat more than three times the global average in meat Lead the world in paper consumption Environment improves with increasing affluence The developed world Affluence in the United States Affluence Affluence in the United States Affluence Enables wealthy to clean up immediate environment by transferring waste to more distant locations. Affluent isolate themselves and unaware of the environmental stresses caused by their consumptive lifestyles. Dynamics of Population Growth Dynamics Population profiles Future populations Population momentum The demographic transition Population Profile United States Population Population Profile United States Population Population Profile United States Population Population Profile of Italy Population Population Profile Italy Population Population Projections United States States Increased fertility rate of 2.0 and current migration Fertility rate of 1.8 Population Profile Developing Country Population Population Profile Developing Country Population Population Momentum Population Effect of current age structures on future population growth. Determined by percent of population in younger versus older age cohorts. World Population Growth and Absolute Growth Absolute Population Momentum Population It will take countries with a large base of younger population a long time to achieve stability. Countries like Iraq will continue to grow for 50­60 years even after the total fertility rate is reduced to replacement level. Calculating Fertility Rates Calculating Crude birth rate (CBR)= no. of live births per 1000 in a population per year Crude death rate (CDR)= no. of deaths per 1000 in a population per year (CBR - CDR)/10 = Rate of Increase or decrease in population per 1000 per year Demographic transition Epidemiologic transition: A reduction in crude death rates (epidemiology is the study of disease) • Medical advances (vaccines, antibiotics) result in reduced crude death rate Demographic transition Fertility transition: A reduction in crude birthrates • Socioeconomic factors result in lower crude birthrates Phases of Demographic Transition Transition Phases of Demographic Transition Transition Phase I: primitive stability • Crude birth rate (CBR) is equal to crude death rate (CDR) CBR = CDR stable population Phases of Demographic Transition Transition Phase II: population explosion • • • declining CDR CBR remains high accelerated population growth. CBR > CDR population increase Phases of Demographic Transition Transition Phase III: • declining fertility rate, but significant population growth continues. Population momentum Phases of Demographic Transition Transition Phase IV: modern stability with low CBR and CDR Demographic Transition Comparisons (Figure 5-17) Comparisons Phase IV: developed countries Phases II and III: developing countries ...
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This note was uploaded on 02/17/2011 for the course BIOL 270 taught by Professor Jones during the Spring '06 term at South Carolina.

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